Method for pulse forming



Dec. 24, 1968 M. J. CARLSON 3,417,456

METHOD FOR PULSE FORMING Filed Sept. 30, 1966 INVENTOR. Melvin J1Gar/son 3 AT ZORNEXS United States Patent Ofice 3,417,456 METHOD FORPULSE FORMING Melvin J. Carlson, Havre De Grace, Md., assignor to theUnited States of America as represented by the Secretary of the ArmyFiled Sept. 30, 1966, Ser. No. 584,064 6 Claims. (Cl. 29-4701) Theproblem of sealing chemical agent munitions has existed for many years.The old methods for performing the function of my invention were byweldingor brazing the workpiece. The surfaces of the workpieces had tobe specially prepared and cleaned. In the case of filling a munitioncontaining receptacle, the workpiece, after being welded, had to becleaned and tested for leaks, followed by annealing to relieve thelocalized stress of the intense heat of the weld. Furthermore, thefiller plug hole had to be drilled and reamed, then the container filledwith a chemical agent, and finally a filler plug presses into place andagain leak tested.

It is also known to form or swage metallic parts by means of highenergy, high speed forming operations such as explosive forming,electrohydraulic forming, pneumatic-mechanical forming and magneticforming.

The advantages of my method and apparatus over the welding operation arethat the method can be used by unskilled labor (i.e. one does not haveto be a skilled welder). The joining operation can be performed inapproximately 1-5 seconds, whereas the welding operation took 3-5minutes. The intense heat of the welding operation is eliminated (i.e.this invention does not generate any heat).

The advantages of my method and apparatus over the prior high energy,high speed forming operations are that these prior operations did notproduce a leak proof seal or rather, the seal failed to pass therigorous helium leak test test forth below.

A further advantage is that close tolerances can be maintained sincethere is no distortion due to any intense heat.

Other advantages of my invention include the fact that non-compatiblemetals and plastics can be joined with a strong leak-proof seal. Onlyone joint, that is to say the final sealing joint, has to be inspectedor leak tested. Thus, it can be seen that my invention is ideally suitedfor mass production of items that have to be joined in a permanent bond.

It is the standard practice of the US. Army when filling chemicalmunitions to exhaust the air and add in the void space over the chemicalagent a helium atmosphere. This helium atmosphere will leak throughminute cracks and faults in the walls of the container, or the sealingof the joint. This is because helium is a monoatomic gas and will passthrough small holes which would not allow a larger molecule such as thechemical agent to pass through. This has the advantage that in storage ahelium leak detector will indicate that some of the chemical munitionsare defective and must be replaced if there is a positive indication ofhelium in the atmosphere. It has been ascertained that when using mymethod and apparatus that the joint or bond obtained will pass the US.Army standard test of having no leakage rate greater than 1 10-cc./second with a helium pressure of 15 p.s.i.g. in the munition.

Other objects and advantages of this invention will become apparent asthe following description is read in connection with the accompanyingdrawing, in which:

FIGURE 1 is a partial cross section of a typical munition using mybonding apparatus and method.

FIGURE 2 shows a typical arrangement of the rocket warhead before thesealing operation.

3 ,417,456 Patented Dec. 24, 1968 FIGURE 3 shows a detail of the bondafter the sealing operation.

Referring now to the drawing, 10 designates the rocket body providedwith a payload containing compartment 12 in which is sealed the chemicalpayload 14. This can be any liquid or solid military chemical agent suchas white phosphorus, or the G-agents (see US. Patent No. 2,867,509). Thecentral burster which is shown at 16 will explode the rocket when theimpact fuse 20 strikes the target area. An insert or plug 18 is providedby which the container 12 is sealed during the course of the bondingprocess.

As a result of my studies of the high energy rate forming processdescribed above, I have discovered that a specific combination or designof rings and grooves are necessary to successfully seal a cylindricalcontainer using this high energy rate forming process. Thus, I havediscovered that it is necessary to provide the plug 18 with threeintegral rings spaced a predetermined distance apart with the centerring 30 of a rectangular cross section and a pair of rings ofright-triangular cross sections 28 and 32, spaced on either side of thecenter ring 30. It is to be noted that the hypotenuse of each of thetriangular cross sections slopes towards the center ring 30. The spacingbetween the rings of triangular cross sections 28 and 32 isapproximately equal to the spacing between the rectangular crosssectional rings 24 of the circular field shaper 22. An insulator 26 isprovided to insulate the metallic components if needed.

In general, I have discovered that the distance from the peak of thetriangular ring 28 or 32 to the bottom of the groove should beapproximately 1-3 times the thickness of the cylindrical container 12.Likewise, the distance from the peak of the triangular groove 28 or 32to the top of the rectangular central ring 30 should be approximatelyone-half the thickness of the cylindrical container or workpiece 12. Thedistance between the peaks of the triangular rings 28 and 32 should beapproximately 5-10 times the thickness of the cylindrical container 12.Obviously, the distance between rings 24 should be the same as thedistance between rings 28 and 32. The shape of the triangular rings 28and 32 must have a general shape shown on the drawing (i.e. anapproximately 45 angle at the peak). Substantially the same results willbe obtained with an angle of 405'0; however, I prefer the 45 angle as itgives the best results. These results are that a leak tight diffusionbond between the plug 18 and the container 12 results where thetriangular ring is impacted into the cylindrical container. In thecenter of the bonding zone, the rectangular central ring 30 achieves -aform seal in the cylindrical workpiece 12, which gives added strength tothe bond.

In general, my process consists of first fabricating the plug 18 so asto provide three integral rings as set forth above. This can be done byany conventional machining technique such as using milling cutters ofthe desired configurations or by turning on an engine lathe. The partsto be assembled are merely wiped clean. The next step is to assemble thecomponents in the high energy rate forming machine or device which hasthe two spaced rings 24 of a rectangular cross section. The final stepis to subject my specific configuration to a high energy rate formingprocess such as an explosive impulse, a high speed ram, and a supermagnet such as the Magneform machine. These high energy rate formingprocesses exceeding 50,000 lbs. per square inch (generally in the rangeof 50,000750,000 p.s.i.) in micro seconds and are responsible for thedesired diffusion bonding of my particular design. The resulting bond isas good as or better than the welding operation with the advantage thatno heat is produced and the bonding operation is accomplished in a muchshorter time. For convenience and speed of operation, we have found theMagneform machine to be superior to the other methods which, however,produce a bond which is equally desirable.

Obviously, my invention can be applied to the sealing of any containerwhere it is desired to permanently seal ,a chemical or biologicalmaterial. Hence, my invention has both military and commercialapplications.

I have disclosed my invention with a limited number of embodiments.Obviously, it is possible for a person skilled in the art to produceother variations without departing from the inventive concept disclosedherein. Therefore it is desired that only such limitation be imposed onthe appended claims as are stated therein or are required by the priorart.

I claim:

1. A method of joining a tubular workpiece selected from metal andplastic material to a cylindrical workpiece selected from metal andplastic material comprising the steps of i (a) fabricating said tubularworkpiece so as to provide three integral rings spaced a predetermineddistance apart, with a center ring of a rectangular cross section havinga top and a pair of rings of a right trianguler cross section eachhaving a peak spaced on either side of said center ring in a manner suchthat the hypotenuse of each of said triangular cross sections slopestowards said center ring, the distance from each said peak of thetriangular rings and said top of the rectangular ring beingapproximately onehalf the thickness of the cylindrical workpiece,

(b) inserting said tubular workpiece into said cylindrical workpiece,assembling the workpieces in a high energy rate forming machine, saidmachine having a pair of rings located above each said peak of saidtriangular rings and joining said tubular workpiece to said cylindricalworkpiece by means of a high energy, high speed impulse. 2. The methodset forth in claim 1 whereby said tubular workpiece is milled to providethree integral rings.

3. The method set forth in claim 1 whereby said tubular workpiece isturned so as to provide three integral rings. 4. The method as set forthin claim 1 in which said tubular workpiece is joined to said cylindricalworkpiece by means of a high energy, high speed magnetic pulse. 5. Themethod set forth in claim 1 in which said tubular workpiece is joined tosaid cylindrical workpiece by means of an explosive pulse.

' 6. The method as set forth in claim 1 in which said tubular workpieceis joined to said cylindrical workpiece by means of a high speed, highenergy hydraulic pulse.

References Cited UNITED STATES PATENTS 1,163,784 12/1915 Skinner 29-5211,179,853 4/1916 McCulloch 29-516 XR 2,289,271 7/1942 Kane 29-4705 X3,106,014 10/1963 Brick 29-475 X 3,149,372 9/1964 Stinger.

3,203,212 8/1965 Simicich 72-56 3,208,254 9/1965 Inoue 7256 3,364,5621/1968 Armstrong 29-482 X 3,371,404 3/1968 Lemelson 29-421 JOHN F.CAMPBELL, Primary Examiner.

R. F. DROPKIN, Assistant Examiner.

US. Cl. X.R.

1. A METHOD OF JOINING A TUBULAR WORKPIECE SELECTED FROM METAL ANDPLASTIC MATERIAL TO A CYLINDRICAL WORKPIECE SELECTED FROM METAL ANDPLASTIC MATERIAL COMPRISING THE STEPS OF: (A) FABRICATING SAID TUBULARWORKPIECE SO AS TO PROVIDE THREE INTEGRAL RINGS SPACED A PREDETERMINEDDISTANCE APART, WITH A CENTER RING OF A RECTANGULAR CROSS SECTION HAVINGA TOP AND A PAIR OF RINGS OF A RIGHT TRIANGULER CROSS SECTION EACHHAVING A PEAK SPACED ON EITHER SIDE OF SAID CENTER RING IN A MANNER SUCHTHAT THE HYPOTENUSE OF EACH OF SAID TRIANGULAR RINGS AND SAID TIONSSLOPES TOWARDS SAID CENTER RING, THE DISTANCE FROM EACH SAID PEAK OF THETRIANGULAR RINGS AND SAID TOP OF THE RECTANGULAR RING BEINGAPPROXIMATELY ONEHALF THE THICKNESS OF THE CYLINDRICAL WORKPIECE, (B)INSERTING SAID TUBULAR WORKPIECE INTO SAID CYLILNDRICAL WORKPIECE,ASSEMBLING THE WORKPIECES IN A HIGH ENERGY RATE FORMING MACHINE, SAIDMACHINE HAVING A PAIR OF RINGS LOCATED ABOVE EACH SAID PEAK OF SAIDTRIANGULAR RINGS AND JOINING SAID TUBULAR WORKPIECE TO SAID CYLINDRICALWORKPIECE BY MEANS OF A HIGH ENERGY, HIGH SPEED IMPULSE.